Where are you based? Send it in for repair under warranty, but if you have a sentiment attachment to it, remember to let them know, else they might send you a brand new one.
I think the only way would be to disassemble the handle. Then you might be able to add something to the back of the lock to make better contact. If it was me I might try to slip something between the lock and the spring to see if that would work before taking it apart.
The only way I see is a disassembly so you have the faulty bare handle seperately without tools.To remove the lock rocker you'll have to push/pull the handle to widen the space that holds the lock rocker in place.The metal is springy a bit but you might end up having to bend it open to get the lock rocker out.
If I am reading correctly, the pin that u are referring to is not a pin. It's a whole piece together with the locking tab. U will need to unscrew that end, dig out that locking tab to be able to access and bend the spring back. Be careful when bending though cos that may break..